It is well known that the compressibility of crushable granular materials increases with the moisture content,due to the decrease of particle strength in a humid environment.An existing approach to take into account t...It is well known that the compressibility of crushable granular materials increases with the moisture content,due to the decrease of particle strength in a humid environment.An existing approach to take into account the effect of grain breakage in constitutive modeling consists in linking the evolution of the grain size distribution to the plastic work.But how the material humidity can affect this relationship is not clear,and experimental evidence is quite scarce.Based on compression tests on dry and saturated crushable sand recently reported by the present authors,a new non-linear relationship is proposed between the amount of particle breakage and the plastic work.The expression contains two parameters:(1)a material constant dependent on the grain characteristics and(2)a constant depending on the wetting condition(in this study,dry or saturated).A key finding is that the relationship does not depend on the stress path and,for a given wetting condition,only one set of parameters is necessary to reproduce the results of isotropic,oedometric,and triaxial compression tests.The relationship has been introduced into an elastoplastic constitutive model based on the critical state concept with a double yield surface for plastic sliding and compression.The breakage ratio is introduced into the expression of the elastic stiffness,the critical state line and the hardening compression pressure.Incremental stress-strain computations with the model allow the plastic work to be calculated and,therefore,the evolution of particle crushing can be predicted through the proposed non-linear relationship and reintroduced into the constitutive equations.Accurate predictions of the experimental results in terms of both stress-strain relationships and breakage ratio were obtained.展开更多
This study proposes an approach that considers mitigation strategies in predicting landslide susceptibility through machine learning(ML)and geographic information system(GIS)techniques.ML models,such as random forest(...This study proposes an approach that considers mitigation strategies in predicting landslide susceptibility through machine learning(ML)and geographic information system(GIS)techniques.ML models,such as random forest(RF),logistic regression(LR),and support vector classification(SVC)are incorporated into GIS to predict landslide susceptibilities in Hong Kong.To consider the effect of mitigation strategies on landslide susceptibility,non-landslide samples were produced in the upgraded area and added to randomly created samples to serve as ML models in training datasets.Two scenarios were created to compare and demonstrate the efficiency of the proposed approach;Scenario I does not considering landslide control while Scenario II considers mitigation strategies for landslide control.The largest landslide susceptibilities are 0.967(from RF),followed by 0.936(from LR)and 0.902(from SVC)in Scenario II;in Scenario I,they are 0.986(from RF),0.955(from LR)and 0.947(from SVC).This proves that the ML models considering mitigation strategies can decrease the current landslide susceptibilities.The comparison between the different ML models shows that RF performed better than LR and SVC,and provides the best prediction of the spatial distribution of landslide susceptibilities.展开更多
In this paper we present recent developments concerning a Cell-Centered Arbitrary Lagrangian Eulerian(CCALE)strategy using the Moment Of Fluid(MOF)interface reconstruction for the numerical simulation of multi-materia...In this paper we present recent developments concerning a Cell-Centered Arbitrary Lagrangian Eulerian(CCALE)strategy using the Moment Of Fluid(MOF)interface reconstruction for the numerical simulation of multi-material compressible fluid flows on unstructured grids in cylindrical geometries.Especially,our attention is focused here on the following points.First,we propose a new formulation of the scheme used during the Lagrangian phase in the particular case of axisymmetric geometries.Then,the MOF method is considered for multi-interface reconstruction in cylindrical geometry.Subsequently,a method devoted to the rezoning of polar meshes is detailed.Finally,a generalization of the hybrid remapping to cylindrical geometries is presented.These explorations are validated by mean of several test cases using unstructured grid that clearly illustrate the robustness and accuracy of the new method.展开更多
The parameters obtained from oedometric consolidation tests are commonly used in the development of constitutive modeling and for engineering practice. This paper focuses on the influence of the natural deposition pla...The parameters obtained from oedometric consolidation tests are commonly used in the development of constitutive modeling and for engineering practice. This paper focuses on the influence of the natural deposition plane orientation on oedometric consolidation behavior of three natural clays from the southeast coast of China. Oedometer tests were conducted on intact specimens prepared by sampling at a series of angles relative to the natural deposition plane. For each specimen, yield stress,compressibility indexes, secondary compression, and permeability coefficients were determined. The influence of the sampling angle on these properties was investigated, revealing that yield stress, compression index, swelling index, creep index, ratio of secondary compression coefficient to compression index(Cae/Cc) and permeability coefficient were all dependent to some extent on the sampling angle. These findings indicate the role of the anisotropy due to the natural deposition on the oedometric consolidation behavior.展开更多
One can compute the final deformation of a known geometry under specific boundary conditions using the constitutive laws of mechanics that describe their stress strain behavior.In such cases the initial geometry is kn...One can compute the final deformation of a known geometry under specific boundary conditions using the constitutive laws of mechanics that describe their stress strain behavior.In such cases the initial geometry is known,and all operators mapping the deformation are defined on the reference domain.However,there are situations in which the final configuration of a deformation might be known but not the initial.The inverse formulation allows one to determine the initial geometry of a domain,given its final deformation state,the material behavior law and a set of boundary conditions.In the present work we propose a method to reconstruct the mesoscale geometry of a textile based on its mechanical response during compaction.To do so,stress boundary conditions are acquired by means of a pressuresensitive film.By adopting an appropriate material law,the thickness and width information of the yarns are deduced from the pressure field experienced by the compacted textile.Unlike 3 D scanning techniques such as-CT,the proposed method can be applied on any domain size,allowing long-range variability to be captured.To the best of the authors’knowledge,there are no previous works that use a pressure-sensitive film on a large domain to capture the input data for a shape reconstruction.This example application serves as a demonstration of a methodology which could be applied to other classes of materials.展开更多
基金financial support of CONICYT Chile through project FONDECYT 11150084
文摘It is well known that the compressibility of crushable granular materials increases with the moisture content,due to the decrease of particle strength in a humid environment.An existing approach to take into account the effect of grain breakage in constitutive modeling consists in linking the evolution of the grain size distribution to the plastic work.But how the material humidity can affect this relationship is not clear,and experimental evidence is quite scarce.Based on compression tests on dry and saturated crushable sand recently reported by the present authors,a new non-linear relationship is proposed between the amount of particle breakage and the plastic work.The expression contains two parameters:(1)a material constant dependent on the grain characteristics and(2)a constant depending on the wetting condition(in this study,dry or saturated).A key finding is that the relationship does not depend on the stress path and,for a given wetting condition,only one set of parameters is necessary to reproduce the results of isotropic,oedometric,and triaxial compression tests.The relationship has been introduced into an elastoplastic constitutive model based on the critical state concept with a double yield surface for plastic sliding and compression.The breakage ratio is introduced into the expression of the elastic stiffness,the critical state line and the hardening compression pressure.Incremental stress-strain computations with the model allow the plastic work to be calculated and,therefore,the evolution of particle crushing can be predicted through the proposed non-linear relationship and reintroduced into the constitutive equations.Accurate predictions of the experimental results in terms of both stress-strain relationships and breakage ratio were obtained.
基金funding by the National Natural Science Foundation of China(Grant No.42007416)the Hong Kong Polytechnic University Strategic Importance Fund(ZE2T)and Project of Research Institute of Land and Space(CD78).
文摘This study proposes an approach that considers mitigation strategies in predicting landslide susceptibility through machine learning(ML)and geographic information system(GIS)techniques.ML models,such as random forest(RF),logistic regression(LR),and support vector classification(SVC)are incorporated into GIS to predict landslide susceptibilities in Hong Kong.To consider the effect of mitigation strategies on landslide susceptibility,non-landslide samples were produced in the upgraded area and added to randomly created samples to serve as ML models in training datasets.Two scenarios were created to compare and demonstrate the efficiency of the proposed approach;Scenario I does not considering landslide control while Scenario II considers mitigation strategies for landslide control.The largest landslide susceptibilities are 0.967(from RF),followed by 0.936(from LR)and 0.902(from SVC)in Scenario II;in Scenario I,they are 0.986(from RF),0.955(from LR)and 0.947(from SVC).This proves that the ML models considering mitigation strategies can decrease the current landslide susceptibilities.The comparison between the different ML models shows that RF performed better than LR and SVC,and provides the best prediction of the spatial distribution of landslide susceptibilities.
文摘In this paper we present recent developments concerning a Cell-Centered Arbitrary Lagrangian Eulerian(CCALE)strategy using the Moment Of Fluid(MOF)interface reconstruction for the numerical simulation of multi-material compressible fluid flows on unstructured grids in cylindrical geometries.Especially,our attention is focused here on the following points.First,we propose a new formulation of the scheme used during the Lagrangian phase in the particular case of axisymmetric geometries.Then,the MOF method is considered for multi-interface reconstruction in cylindrical geometry.Subsequently,a method devoted to the rezoning of polar meshes is detailed.Finally,a generalization of the hybrid remapping to cylindrical geometries is presented.These explorations are validated by mean of several test cases using unstructured grid that clearly illustrate the robustness and accuracy of the new method.
基金Project supported by the National Natural Science Foundation of China(Nos.41240024 and 41372285)the Shanghai Pujiang Talent Plan(No.11PJ1405700)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China(No.20110073120012)the European Project CREEP(No.PIAPP-GA-2011-286397)
文摘The parameters obtained from oedometric consolidation tests are commonly used in the development of constitutive modeling and for engineering practice. This paper focuses on the influence of the natural deposition plane orientation on oedometric consolidation behavior of three natural clays from the southeast coast of China. Oedometer tests were conducted on intact specimens prepared by sampling at a series of angles relative to the natural deposition plane. For each specimen, yield stress,compressibility indexes, secondary compression, and permeability coefficients were determined. The influence of the sampling angle on these properties was investigated, revealing that yield stress, compression index, swelling index, creep index, ratio of secondary compression coefficient to compression index(Cae/Cc) and permeability coefficient were all dependent to some extent on the sampling angle. These findings indicate the role of the anisotropy due to the natural deposition on the oedometric consolidation behavior.
基金partially funded by Conseil Regional Pays de la Loire(grant number TEU29)。
文摘One can compute the final deformation of a known geometry under specific boundary conditions using the constitutive laws of mechanics that describe their stress strain behavior.In such cases the initial geometry is known,and all operators mapping the deformation are defined on the reference domain.However,there are situations in which the final configuration of a deformation might be known but not the initial.The inverse formulation allows one to determine the initial geometry of a domain,given its final deformation state,the material behavior law and a set of boundary conditions.In the present work we propose a method to reconstruct the mesoscale geometry of a textile based on its mechanical response during compaction.To do so,stress boundary conditions are acquired by means of a pressuresensitive film.By adopting an appropriate material law,the thickness and width information of the yarns are deduced from the pressure field experienced by the compacted textile.Unlike 3 D scanning techniques such as-CT,the proposed method can be applied on any domain size,allowing long-range variability to be captured.To the best of the authors’knowledge,there are no previous works that use a pressure-sensitive film on a large domain to capture the input data for a shape reconstruction.This example application serves as a demonstration of a methodology which could be applied to other classes of materials.